Research areas of the Institute of Physical Chemistry

The research activities of the Physical Chemistry Institute are situated at the boundary between chemistry, physics, and material science, following a long tradition of physical chemistry of soft condensed matter at the University of Cologne. The different modes of correlation and interaction between the building blocks of matter on the molecular and mesoscopic level are essential for materials performance, and we are concerned with the relationships between the molecular structure of matter and the resulting physical properties.

Starting on the molecular level, the group of Ulrich Deiters uses methods of statistical thermodynamics, particularly computer simulations, to study intermolecular interactions as well as equilibrium and transport phenomena in fluids and fluid mixtures. Building on this, prediction methods for thermodynamic properties are developed, particularly for phase equilibria at high pressures. The formation kinetics of nanoparticles, especially in supercritical fluids, is addressed by Thomas Kraska using molecular dynamics simulation techniques.

Transport phenomena and electronic properties in (macro-) molecular layers and organic semiconductors and their correlation with structural parameters are a main issue in the group of Klaus Meerholz. Organic electronic devices developed in his team include organic light–emitting diodes, solar cells, transistors, organic memory, and sensors. The underlying photophysical processes and charge transport mechanism in organic-electronic materials and devices are addressed by optical and electrochemical methods. In particular, the occurrence and nature of triplet states are investigated by time-resolved laser spectroscopy under responsibility of Dirk Hertel. Photoelectron spectroscopic methods and their advancement for the energy level alignment in organic electronic devices is advanced by Selina Olthof. At the same time, novel processing and coating techniques are developed in the Meerholz lab. The group activities at the cutting edge of organic electronics have gained prominent visibility – manifested in prestigious projects like COPT.NRW, and the 2014 Max Delbrück Award of the University of Cologne for Prof. Meerholz.

The research of Klas Lindfors concentrates on the ultrafast optical spectroscopy of nanostructures. Of particular interest is the optical response of hybrid nanostructures combining plasmon resonant metal nanostructures with semiconductor heterostructures, organic light emitters, and nonlinear optical materials. The group combines high-resolution optical microscopy with luminescence, scattering, and transmission spectroscopy as well as nonlinear optical techniques to study light-matter interaction in single nanostructures. The absence of ensemble averaging allows probing the details of the interplay of light and matter on the nanoscale.

The structure and dynamics of soft matter, specifically the development of nanostructured, complex materials from organic and inorganic components, is a main issue in the group of Annette Schmidt. Using quasi-static and dynamic methods including rheology, light scattering, magnetometry, and dark field scattering microscopy, the modes and time scale of interaction between the components are investigated. The results are of significance for the development of self-healing polymers, for locomotion and transport strategies at low Reynolds numbers, and for adaptive systems based on responsive soft matter and functional polymers. The field- and template-assisted self-assembly of dipolar nanostructures into highly ordered layers, and the resulting cooperative properties are addressed in the group of Sabrina Disch.

Presently the research of Simone Wiegand focuses on the understanding of hydrogen bonds, which are essential for life on earth. She studies transport processes in aqueous systems, which are influenced by changes of the hydration layer, using optical and scattering methods under isothermal conditions and in temperature gradients. In the recent years it has been demonstrated that the transport in a temperature gradient is very sensitive to changes of the hydration layer and can be used to monitor biochemical and pharmaceutical reactions. Additionally, it turned out that the so-called thermophoresis plays an important role in the “origin-of-life” scenario.

Overall, the institute significantly contributes to the material science focus of the Chemistry Department, and several groups (Meerholz, Schmidt, Lindfors, Disch, Hertel) are engaged in the UzK Center of Competence "Quantum Matter and Materials" (QM2). Further cooperation involves other groups from chemistry, physics, biology, engineering, and medicine at the UoC and beyond, strong conjunctions to the Forschungszentrum Jülich, in particular the Institutes for Complex Systems 1-3, and the IHRT graduate school BioSoft.